1. Field of Invention
The present invention relates to a light emitting device, surface light source device, display and a light flux control member, being applied, for example, to a light emitting device or surface light source device 2 for backlighting a display member such as LCD-panel, or to a display composed of a display member and such light emitting device or surface light source device.
Further, the present invention is also applied to a light flux control member used in devices as above. More concretely, a light emitting device, surface light source device, display and light flux control member are employable in displays used as TV-monitors or monitors for personal computers and in backlighting arrangements in the devices. In addition, applications to interior illumination or various illumination are possible.
2. Related Arts
It has been known to employ a surface light source device provided with a light emitting diode (LED) and a plate-like light flux control member, as illumination means for LCD-monitors used in personal computers, TV-sets or the likes. Usually a plurality of LEDs are employed and arranged like a matrix at a back side of a light flux control member. Light from the LEDs enters into the light flux control member through a back face thereof, being emitted from an emission face opposite to the back face. Then a LCD-panel is backlighted by the emitted light . FIG. 19 illustrates an example of display to which such prior arts are applied, being disclosed, for example, in Document 1 noted below. Referring to FIG. 19, conventional display 100 is provided with a light diffusing member (light flux control member) 121, substrate 101 arrange along an inner face of light diffusing 121, a plurality of LEDs (point-like light emitting elements) 120 disposed on substrate 101 at a predetermined pitch and display member (such as LED- panel).
Light from the respective LEDs enters into light diffusing member 121 through an inner face thereof, becoming inner propagation light. This inner propagation light is outputted from an emission face provided by an outer face (i.e. a face opposite to the inner face) of light diffusing member 121, being supplied to a display (such as LCD-panel) 3.                Document 1; Tokkai-Hei 7-191311        
However, conventional display 100 gives a large difference in illuminance between locations near to an optical axis of LED 120 and locations far from the optical axis, resulting in being difficult to illuminate display member 3. That is, an illuminance curve of output illumination light shows a conspicuous wave-like undulation corresponding to locations of LEDs 120, as described later by referring to FIGS. 10, 11, 15 and 17. In general, such uneven brightness is not desirable.